Honeycomb body with internal leading edges, in particular a catalyst body for motor vehicles

ABSTRACT

A honeycomb body, especially a catalyst carrier body, includes at least partly structured metal sheets forming walls of a plurality of channels through which a fluid can flow. Some of the sheets have a primary corrugation with crests, troughs and a given corrugation height. The crests and/or the troughs having a plurality of inverted regions with a height being at most equal to the given corrugation height and preferably between 1/3 and 2/3 of the given corrugation height.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a honeycomb body, in particular a catalyst bodyfor motor vehicles, including at least partly textured layered metalsheets forming walls of a plurality of channels through which a fluidcan flow.

2. Description of Related Art

Many embodiments of metal catalyst carrier bodies of such a type areknown and are described, for instance, in Published European ApplicationNos. 0 220 468 A1, corresponding to U.S. Pat. No. 4,878,746; 0 279 159A1, corresponding to U.S. Pat. No. 4,845,073; 0 245 737 A1,corresponding to U.S. Pat. No. 4,832,998; or 0 245 736 A1.

It has long been known that in most applications and given the usualdimensions of such honeycomb bodies, the flow in the channels isessentially laminar, because very small channel cross sections are used.Under such conditions, relatively thick boundary layers form at thechannel walls, which reduce contact between the core flow in thechannels and the walls. Processes of diffusion between the core flow andthe boundary layer partly balance this out, but still attempts have longbeen made to gain improvements with such devices by means of specialstructuring of the honeycomb body.

For instance, it is known from German Patent No. DE-PS 1 192 624,corresponding to U.S. Pat. No. 3,208,131, to make the honeycomb bodyfrom a large number of disks that are disposed in succession and havethe channels which are offset from one another in the flow direction. Abody that is constructed in that way has a succession of new leadingedges in the interior thereof, at which the flow is split. Preferably,disks made of spirally rolled smooth and corrugated metal sheets areused in succession, with the direction of rolling being changed eachtime. On one hand, such a structure is very expensive from a productionstandpoint because of the many small disks, and on the other hand itleads to irregular configurations of the channels that are offset fromone another, which can be disadvantageous during the coating operationand during later operation.

In Published European Application Nos. 0 152 560 A1 and 0 186 801 A2,possibilities for achieving the same concept are described that are moreadvantageous in production terms, because they do not require assemblyof a honeycomb body from a plurality of disks. However, the undulatingforms described therein do result in considerable proportions of thesurface area of the metal sheets being used contacting one another, andas a result the usable area for catalytic contacting is disadvantageousin proportion to the amount of material being used.

In a survey article by M. Nonnenmann, entitled "Neue Metalltrager furAbgaskatalysatoren mit erhohter Aktivitat und inneremStromungsausgleich" [New Metal Carriers for Exhaust Gas Catalysts ThatHave Increased Activity and Internal Flow Equalization] ATZAutomobiltechnische Zeitschrift [Automobile Industry Journal] 91 (1989),4, pp. 185-192, describing the advantages and effects of flow channelsthat are offset from one another in the flow direction, a variant isalso proposed in which instead of a smooth sheet metal layer, aso-called micro-corrugated strip is used, which makes for somewhat moreadvantageous utilization of the surface area. However, amicro-corrugation strip, along with smooth contacting surfaces, formstiny channels on other structured sheet-metal strips, which becomeclogged during a later coating operation and thus result in aconsiderable increase in pressure loss and a further increase in activesurface area as well as an unnecessary consumption of coatingcomposition. Nevertheless, the article shows that because of theproduction options, a metal catalyst carrier body is superior to anextruded ceramic body, because the flow conditions in the interior canbe influenced by structural provisions. An additional effect can arise,namely the transverse mixing of flows in the various channels throughcorresponding connecting paths or openings in the channel walls.

SUMMARY OF THE INVENTION

It is accordingly an object of the invention to provide a honeycomb bodywith internal leading edges, in particular a catalyst body for motorvehicles, which overcomes the hereinafore-mentioned disadvantages of theheretofore-known devices of this general type, in which the advantagesof internal walls being offset from one another can be exploited and inwhich only small portions of the surface area of the individual layerscontact one another. Aspects having to do with manufacturing techniquesshould also be taken into account, in order to keep down the expense forproducing such honeycomb bodies.

With the foregoing and other objects in view there is provided, inaccordance with the invention, a honeycomb body, especially a catalystcarrier body, comprising at least partly structured metal sheets formingwalls of a plurality of channels through which a fluid can flow, some ofthe sheets having a primary corrugation with crests, troughs and a givenpredetermined corrugation height, and the crests and/or the troughshaving a plurality of inverted regions or eversions with a height beingless than or equal to the given corrugation height, and preferablybetween 1/3 and 2/3 of the given corrugation height.

A honeycomb body of this kind is particularly suitable as a catalystcarrier body, preferably for motor vehicles equipped with internalcombustion engines. The inverted regions create additional leading edgesin the interior of the honeycomb body and together with the primarycorrugations form a structure that lessens the formation of boundarylayers as a fluid flows through them. Such a body has a higher catalyticconversion rate, for the same consumption of material, thancorresponding bodies lacking inverted regions. If the structured sheetsare disposed in layers, the areas of contact between the individuallayers are also reduced in size by the inverted regions.

Considering the flow conditions in such a honeycomb body, in accordancewith another feature of the invention, the inverted regions have alength of approximately 4 to 20 mm, and preferably 8 to 16 mm, so thatif at all possible closed boundary layers cannot even form.

In accordance with a further feature of the invention, at least two ofthe inverted regions are formed in succession on each crest and/or eachtrough in the flow direction, in order to create repeatedly newadditional leading edges.

In accordance with an added feature of the invention, the spacingbetween two successive inverted regions on a crest or trough is on thesame order of magnitude as the length of the inverted regions, that isapproximately 4 to 20 mm and preferably 8 to 16 mm.

Depending on the depth of the inverted regions, they can be locateddirectly beside one another both on a crest and in a trough. However,for the sake of stability, it is more advantageous if, in accordancewith an additional feature of the invention, the inverted regions in thecrests are shifted in a flow direction with respect to the invertedregions in the troughs by an offset of substantially between 0 and 30mm, and preferably the offset is greater than the length of the invertedregions.

In order to create even more leading edges in a honeycomb body that arenot in alignment with one another, in accordance with yet an otherfeature of the invention, at least two inverted regions are formed atdifferent heights on each crest and/or each trough. While using the sameamount of material, additional leading edges are thus created, making afictitious subdivision of the honeycomb body as if the body had a muchgreater number of channels than there are crests and troughs of theprimary corrugation.

In principle, the form of a primary corrugation and that of the invertedregion is not critical, as long as the primary corrugation does not haveoverly flat crests and troughs that could form large contacting surfaceswith adjacent layers.

In accordance with yet a further feature of the invention, the primarycorrugation is a zig-zag corrugation with slightly rounded crests andtroughs, which produces very simple geometric conditions in terms of theinverted region and the resultant channel shapes.

In accordance with yet an added feature of the invention, the primarycorrugation is equivalent to the developed view of an involute gear, asis also known from the above-discussed prior art, which is advantageousfrom the standpoint of manufacturing techniques and has high elasticity.

In accordance with yet an additional feature of the invention, theinverted regions themselves are approximately V-shaped or U-shaped,optionally with rounded edges or transitions to the primary corrugation.

In accordance with again another feature of the invention, the invertedregions are approximately equivalent to the shape of the teeth of aninvolute gear.

In a particular feature of the invention, the inverted regions can alsovary the flow course, by providing that the lateral surfaces of theinverted regions do not extend parallel to the flow. This can beattained, for instance, by means of different heights of eachprotuberance on both end surfaces, or by means of a slightly obliqueposition with respect to the center lines of the channels. This versionis advantageous in combination with optional openings in possibleintermediate layers. Therefore, in accordance with again a furtherfeature of the invention, the inverted regions have ends with differentheights and wall surfaces extending at an acute angle relative to thedirection of the channels defined by the primary corrugation.

In accordance with again an added feature of the invention, there areprovided end surfaces, the inverted regions having a quantity per unitof volume increasing from one of the end surfaces to the other as seenin the direction of the channels formed by the primary corrugation. Forthe sake of temperature distribution in the honeycomb body, it may alsobe suitable not to distribute the inverted regions uniformly but insteadto have the number of the inverted regions per unit of volume increasein the flow direction. This has an effect similar to that of a honeycombbody structure made of disks, in which the number of channels increasesin the flow direction per unit of cross-sectional area.

In accordance with again an additional feature of the invention, thesheets are alternating layers of smooth or slightly structured andcorrugated sheets having the inverted regions and being rolled, stackedor coiled together.

Metal sheets according to the invention that are corrugated withinverted regions, are suitable for practically all known productionmethods that were formerly applicable to merely corrugated sheets. Forinstance, bodies can be assembled from stacks of sheets with oppositelycoiled ends or from folded stacks of sheets that are coiled around oneanother. The term "slightly structured sheet layer" is intended to referto a sheet layer that is corrugated with only a slight amplitude incomparison with the primary corrugation and/or a sheet layer structuredwith a slight amplitude transversely to the flow direction which,however, in contrast to the primary corrugation, does not primarilydetermine the size of the resultant channels in the honeycomb body.

In accordance with still another feature of the invention, the smooth orslightly structured sheet layers have openings formed therein. This isdone in order to promote an additional transverse mixing in thehoneycomb body. This reduces the virtually linear contact surfacesbetween the smooth and corrugated sheet layers even further, so that thematerial being used is exploited particularly advantageously forcatalytically active surfaces.

Any other features known for improving elasticity, storability,effectiveness and ease of production in metal honeycomb bodies cansubstantially be adapted for the present invention.

In particular, in accordance with still a further feature of theinvention, the crests and the troughs have narrow contact surfacescontacting the smooth sheets.

In accordance with a concomitant feature of the invention, the contactsurfaces have at least some regions being brazed or soldered to oneanother.

It is also possible to attach the sheet layers to a jacket tubesurrounding the honeycomb body by using joining techniques.

Other features which are considered as characteristic for the inventionare set forth in the appended claims.

Although the invention is illustrated and described herein as embodiedin a honeycomb body with internal leading edges, in particular acatalyst body for motor vehicles, it is nevertheless not intended to belimited to the details shown, since various modifications and structuralchanges may be made therein without departing from the spirit of theinvention and within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however,together with additional objects and advantages thereof will be bestunderstood from the following description of specific embodiments whenread in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary, diagrammatic, perspective view of a small pieceof a corrugated metal sheet provided with inverted regions in accordancewith the invention;

FIG. 2 is a fragmentary end view of a sheet layer of a honeycomb bodyprovided with inverted regions in accordance with the invention;

FIG. 3 is a view similar to FIG. 2 of one layer of a honeycomb bodyaccording to the invention having two inverted regions of differentheights; and

FIG. 4 is a fragmentary, cross-sectional view of a portion of a layer ofa honeycomb body according to the invention having a different form ofprimary corrugation and of the inverted regions.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the figures of the drawing in detail and first,particularly, to FIG. 1 thereof, there is seen a small piece of astructured metal sheet 1, which is provided with inverted regions 4 oncrests 2 and inverted regions 5 on troughs 3. Honeycomb bodies accordingto the invention can be produced from metal sheets being structured inthis way, preferably in combination with smooth sheets as intermediatelayers, by stacking, rolling or coiling stacks of metal sheets in amanner that is known per se. The inverted regions 4, 5 produceadditional leading edges 6 in the interior of such a honeycomb body,thereby considerably improving its efficiency without increasing theconsumption of material. The inverted regions 4 and 5 have respectiveheights h and h'. In contrast to a corrugation height H, the dimensionalaccuracy of the heights of the inverted regions 4, 5 is not critical, sothat in principle the various inverted regions 4, 5 can also havedifferent heights. A typical corrugation height H for the primarycorrugation is approximately 2 to 5 mm. The heights h, h' of theinverted regions should preferably be at least slightly less than thecorrugation height H, so that the inverted regions do not protrude pastthe crests 2 and troughs 3, which would prevent stacking or rolling at adefined spacing. It should also not be possible for bridges to formbetween the inverted regions and adjacent layers in a coating operation.The length a of an inverted region may be between 4 and 20 mm andpreferably approximately 8 to 16 mm. A plurality of inverted regions 4,5 should follow one another at equal spacings on a respective crest 2 ortrough 3, that is at distances b of from 4 to 20 mm and preferably 8 to16 mm. For the sake of stability, it is preferable not to have invertedregions 4 of crests 2 located immediately adjacent to inverted regions 5of troughs 3, although this is possible in principle. An offset c in theflow direction of up to 30 mm is structurally suitable. Preferably, theoffset c should in any case be several millimeters greater than thelength a of the inverted regions 4, 5.

FIG. 2 is an end view of part of a layer of a honeycomb body accordingto the invention, which is shown diagrammatically. A corrugated metalsheet 1, that is located between two adjoining smooth or slightlystructured sheets 10, has a primary corrugation with the height H,having the crests 2 and troughs 3. The inverted regions 4, 5 produce theadditional leading edges 6 in the interior of the honeycomb body. InFIG. 2, the heights h, h' of the inverted regions 4, 5 are smaller thanthe corrugation height H, so that a distance d or d' remains from therespective adjacent smooth or slightly structured sheets 10 to theinverted regions. The distance d, d' should be great enough to preventundesirable bridges of material that later crumble off from beingproduced during subsequent coating of the honeycomb body with a ceramiccomposition. Nevertheless, the leading edges 6 form a structure with aneffect as if the honeycomb body had almost three times as many flowchannels 8 as the crests 2 and troughs 3 of the corrugated sheet. Theeffectiveness in catalytic conversion is correspondingly high, yetwithout having to use an equivalent amount of material.

FIG. 3 is a view comparable to FIG. 2 that shows the effect of invertedregions 4, 4' and 5, 5' of different heights being disposed insuccession. Leading edges are produced that are not in alignment withone another, which lend the honeycomb body greater effectiveness interms of its efficiency than would correspond to the number of flowchannels defined by the corrugated strip 1.

FIG. 4 is a cross section through the region of one layer of a honeycombbody according to the invention, which shows other possible shapes forthe corrugation and inverted regions. A corrugated sheet 41, which islocated between two smooth or slightly structured layers 10 of sheets,has approximately the shape of a developed view of an involute gear.Inverted regions 44, 45 also have the shape of the teeth of an involutegear, with rounded transitions to the primary corrugation. Crests 42 andtroughs 43 may optionally be soldered or brazed to the adjoining smoothsheet layers 10. Additionally, the smooth sheet layers 10 can haveopenings 11 formed therein, which promote a transverse mixing of thefluid flowing in the honeycomb body between the various layers andchannels.

In order to produce a sheet that is corrugated and provided withinverted regions according to the invention as shown in FIG. 1, a smoothsheet-metal strip can first be passed through a pair of corrugatingrollers having the primary corrugation, which is followed by acorrugating step with corrugating rollers having a smaller corrugation7, as suggested in FIG. 1 by broken lines. Each of these rollers onlyworks a portion of the width of the sheet-metal strip 1. Othermanufacturing methods, such as the purposeful folding of a metal sheetwhich is slit at the later leading edges 6, are also possible. Theremaining operating steps in producing a honeycomb body according to theinvention are no different from those of simple corrugated sheets in theprior art.

Due to their reduced weight, the low consumption of material and highefficiency, honeycomb bodies according to the invention are particularlysuitable as catalyst carrier bodies in motor vehicles having internalcombustion engines.

What is claimed is:
 1. Honeycomb body having end surfaces and aninterior, comprising at least partly structured metal sheets formingwalls of a plurality of channels through which a fluid can flow, some ofsaid sheets having a primary corrugation with crests, troughs and agiven corrugation height, and at least one of said crests and saidtroughs having a plurality of inverted regions with a height being atmost equal to said given corrugation height and having a quantity perunit of volume increasing from one of said end surfaces to the other asseen in the direction of said channels formed by said primarycorrugation, said inverted regions defining leading edges in theinterior of the honeycomb body.
 2. Honeycomb body according to claim 1,wherein said height of said inverted regions is between 1/3 and 2/3 ofsaid given corrugation height.
 3. Honeycomb body according to claim 1,wherein said inverted regions have a length being substantially between4 and 20 mm as seen in a flow direction.
 4. Honeycomb body according toclaim 1, wherein said inverted regions have a length being substantiallybetween 8 to 16 mm as seen in a flow direction.
 5. Honeycomb bodyaccording to claim 1, wherein said inverted regions in said crests areshifted in a flow direction with respect to said inverted regions insaid troughs by an offset of substantially between 0 and 30 mm. 6.Honeycomb body according to claim 5, wherein said offset is greater thanthe length of said inverted regions.
 7. Honeycomb body according toclaim 1, wherein each of said crests and each of said troughs have atleast two inverted regions with different heights formed therein. 8.Honeycomb body according to claim 1, wherein said primary corrugationhas an approximately zig-zag shape and said crests and said troughs areslightly rounded.
 9. Honeycomb body according to claim 1, wherein saidprimary corrugation has approximately the shape of a developed view ofan involute gear.
 10. Honeycomb body according to claim 1, wherein saidinverted regions are approximately V-shaped or U-shaped with roundededges or transitions leading to said primary corrugation.
 11. Honeycombbody according to claim wherein said inverted regions are approximatelyin the shape of teeth of an involute gear.
 12. Honeycomb body accordingto claim 1, wherein said inverted regions have ends with differentheights and wall surfaces extending at an acute angle relative to thedirection of said channels defined by said primary corrugation. 13.Honeycomb body according to claim 1, wherein said sheets are alternatinglayers of smooth and corrugated sheets having said inverted regions andbeing rolled, stacked or coiled together.
 14. Honeycomb body accordingto claim 13, wherein said smooth sheets have openings formed therein.15. Honeycomb body according to claim 13, wherein said crests and saidtroughs have narrow contact surfaces contacting said smooth sheets. 16.Honeycomb body according to claim 15, wherein said contact surfaces haveat least some regions being brazed to one another.
 17. Honeycomb bodyaccording to claim 1, wherein said sheets are alternating layers ofslightly structured and corrugated sheets having said inverted regionsand being rolled, stacked or coiled together.
 18. Honeycomb bodyaccording to claim 17, wherein said slightly structured sheets haveopenings formed therein.
 19. Honeycomb body according to claim 1,wherein said metal sheets form catalyst carrier body.
 20. Honeycomb bodyaccording to claim 1, wherein said inverted regions in said crests andsaid troughs are mutually spaced apart by a distance varying fromsubstantially 4 to 20 mm.
 21. Honeycomb body according to claim 1,wherein said inverted regions in said crests and said troughs aremutually spaced apart by a distance varying from substantially 8 to 16mm.
 22. Honeycomb body having an interior, comprising at least partlystructured metal sheets forming walls of a plurality of channels throughwhich a fluid can flow, some of said sheets having a primary corrugationwith crests, troughs and a given corrugation height, each of said crestsand each of said troughs being formed with at least two inverted regionsof different heights being at most equal to said given corrugationheight, and said inverted regions defining leading edges in the interiorof the honeycomb body.
 23. Honeycomb body having an interior, comprisingat least partly structured metal sheets forming walls of a plurality ofchannels through which a fluid can flow, some of said sheets having aprimary corrugation with crests, troughs and a given corrugation height,each of said crests being formed with at least two inverted regions ofdifferent heights being at most equal to said given corrugation height,and said inverted regions defining leading edges in the interior of thehoneycomb body.
 24. Honeycomb body having an interior, comprising atleast partly structured metal sheets forming walls of a plurality ofchannels through which a fluid can flow, some of said sheets having aprimary corrugation with crests, troughs and a given corrugation height,each of said troughs being formed with at least two inverted regions ofdifferent heights being at most equal to said given corrugation height,and said inverted regions defining leading edges in the interior of thehoneycomb body.
 25. Honeycomb body having an interior, comprising atleast partly structured metal sheets forming walls of a plurality ofchannels through which a fluid can flow, some of said sheets having aprimary corrugation with slightly rounded crests and troughs, and withan approximately zig-zag shape and a given corrugation height, at leastone of said crests and said troughs having a plurality of invertedregions with a height being at most equal to said given corrugationheight, and said inverted regions defining leading edges in the interiorof the honeycomb body.
 26. Honeycomb body having an interior, comprisingat least partly structured metal sheets forming walls of a plurality ofchannels through which a fluid can flow, some of said sheets having aprimary corrugation with crests, troughs and a given corrugation height,at least one of said crests and said troughs being formed with aplurality of inverted regions of different heights being at most equalto said given corrugation height, said inverted regions having ends withdifferent heights and wall surfaces extending at an acute angle relativeto the direction of said channels defined by said primary corrugation,and defining leading edges in the interior of the honeycomb body. 27.Honeycomb body according to claim 26, wherein said sheets arealternating layers of smooth sheets having openings formed therein andcorrugated sheets having said inverted regions and being rolled, stackedor coiled together.
 28. Honeycomb body according to claim 26, whereinsaid sheets are alternating layers of slightly structured sheets havingopenings formed therein and corrugated sheets having said invertedregions and being rolled, stacked or coiled together.
 29. Honeycomb bodyhaving an interior, comprising at least partly structured metal sheetsforming walls of a plurality of channels through which a fluid can flow,some of said sheets having a primary corrugation with crests, troughsand a given corrugation height, at least one of said crests and saidtroughs being formed with a plurality of inverted regions of differentheights being at most equal to said given corrugation height, saidsheets being alternating layers of smooth sheets having openings formedtherein and corrugated sheets having said inverted regions and beingrolled, stacked or coiled together, and said inverted regions definingleading edges in the interior of the honeycomb body.
 30. Honeycomb bodyhaving an interior, comprising at least partly structured metal sheetsforming walls of a plurality of channels through which a fluid can flow,some of said sheets having a primary corrugation with crests, troughsand a given corrugation height, at least one of said crests and saidtroughs being formed with a plurality of inverted regions of differentheights being at most equal to said given corrugation height, saidsheets being alternating layers of slightly structured sheets havingopenings formed therein and corrugated sheets having said invertedregions and being rolled, stacked or coiled together, and said invertedregions defining leading edges in the interior of the honeycomb body.